Method and apparatus for cooling a compartment



Fm w EH l W O M C T I! M n D N 1 s m w w July 5, 1968 E. J. KELLY ET AL METHOD AND APPARATUS FOR COOLING A COMPARTMENT Filed Nov. 29, 1963 United States Patent O 3,258,931 METHGD AND APPARATUS FOR COOLING A COMPAR'IMENT Edward J. Kelly, Schuylkill Haven, and Alvin M. Cohodas, Allentown, Pa., assignors to Air Products and Chemicals, Inc., a corporation of Delaware Filed Nov. 29, 1963, Ser. No. 326,889 8 Claims. (Cl. 62-64) The present invention relates to method and apparatus for cooling a compartment, more particularly a compartment of the material storage type having a door that is frequently opened for the purpose of removing material or for the purpose of getting at things in the compartment. The invention will be described and illustrated in connection with a refrigerated truck body, but it is to be specifically understood that the invention is not so limited but is applicable to a wide variety of portable and non-portable compartments. Among the many uses for the present invention other than in connection with truck bodies is the prevention of room temperature aging of solution-heat-treated alloys before fabrication, such as certain aluminum alloys.

Accordingly, it is an object of the present invention to provide methods and apparatus for cooling a compartment, in which a relatively high proportion of the available refrigeration is applied to the material to be refrigerated.

Another object of the present invention is the provision of methods and apparatus for cooling a compartment, in which special provision is made for the safety of persons entering the compartment.

Still another object of the present invention is the provision of methods and apparatus for cooling a compartment, characterized in that improved controls are provided.

Finally, it is an object of the present invention to provide methods and apparatus for cooling a compartment, characterized by relatively lower cost of manufacture, installation and performance, ease, safety and reliability in operation, and ruggedness and durability in use.

Other objects and advantages of the present invention will become apparent from a consideration of the following description, taken in connection with the accompanying drawing, which is a schematic diagram of refrigeration apparatus according to the present invention.

In greater detail, the drawing shows a compartment to be refrigerated indicated at 1, which in the illustrated embodiment represents a truck body of the van truck type. Compartment 1 is designed to be a refrigerated compartment, and is accordingly provided with the usual insulation (not shown). At its rear, compartment 1 has a door 3 that may be opened and closed by the truck driver or other operator.

Disposed in the insulated compartment 1 is a container 5 for a liquefied gas, that is, a gas that is normally in vapor phase at atmospheric temperature and pressure but which is in liquid phase at relatively low temperature. The liquefied gas may for example be liquid nitrogen or liquefied carbon dioxide under relatively high pressure, liquid argon, or other gas. Preferably, the liquefied gas is relatively inert, noncombustible and non-toxic.

Container 5 may be of any suitable material such as stainless steel or other nickel steel or the like, or it may be of glass fiber impregnated with a thermosetting resin such as epoxide, phenol-aldehyde or polyester resin. Resin-impregnated glass fiber has the advantage that it has low specific heat and therefore boils off relatively little liquefied gas when the liquefied gas is first introduced into the relatively warm container, and is also little affected by the thermal shock of introducing relatively cold liquid into a relatively warm container. Whatever its material, container 5 will be surrounded by a suitably 3,258,931 Patented July 5, 1966 thick layer of insulation 7, which may be at atmospheric pressure or evacuated, and may comprise any of the usual insulating materials such as exfoliated vermiculite, ground cork, vapor-deposited metal on plastic film disposed in a multiplicity of layers, powder in vacuum or other suitable insulation.

A fill conduit 9 is provided extending from outside compartment 1 to the interior of compartment 1 and having a checkvalve 11 to prevent vapor or liquefied gas from leaving the compartment through conduit 9. Conduit 9 communicates with a conduit 13 that extends down into container 5 to adjacent the bottom thereof and also extends a substantial distance out of container 5. A vent conduit 15 for gas communicates with an upper portion of container 5. Vent conduit 15 has a branch 17 controlled by a valve 19 for supplying vapor to the interior of the compartment, and a branch 21 controlled by a valve 23 for discharging vapor from an upper portion of container 5 to the outside of the compartment. Valves 19 and 23 are controlled from outside the compartment; and to this end, a conduit 25 bleeds off a small portion of relatively high pressure vapor from vent conduit 15 and supplies it to a control valve 27 with a manual valve actuator disposed outside compartment 1. Valve 27, in turn, communicates with valve 19, which is a diaphragmtype valve that opens under pressure. Valve 19 is provided with a bleed on the control side of its diaphragm, between its diaphragm and valve 27, so that when valve 27 is closed, pressure from vent conduit 25 is cut off from diaphragm valve 19 and the pressure on the control side of the diaphragm quickly bleeds off so that valve 19 closes. When valve 27 is opened, however, then pressure is established above the diaphragm of valve 19 and valve 19 is maintained open. Similarly, valve 23 is a diaphragm-type valve provided with a bleed; and to control it, a conduit 29 conducts relatively high pressure vapor from conduit 25 through a valve 31 to the side of the diaphragm of valve 23 which is opposite the fluid flowing in branch conduit 21. Upon opening of valve 31, the pressure above the diaphragm of valve 23 is increased and valve 23 is accordingly opened; while upon closing valve 31, the pressure bleeds off from above the diaphragm of valve 23 and valve 23 closes. Like valve 27, valve 31 has a manual valve actuator disposed outside the compartment.

In addition to receiving the liquefied gas from a supply (not shown) outside the compartment, conduit 13 serves as a conduit for supplying liquefied gas to the interior of compartment 1. To this end, conduit 13 is provided with a variable control valve 33 that lets down the pressure of liquefied gas passing through it to about or only a little above atmospheric pressure. Downstream of valve 33, conduits 13 and 17 merge in a conduit 35 that leads to a spray header 37 that is disposed along an upper portion of the compartment 1 for the purpose of spraying liquefied gas downwardly into the compartment to cool the compartment by direct heat exchange between liquefied gas and the material to be cooled in the compartment. A control unit 39 variably controls the opening and closing of valve 33 pneumatically. Specifically, control valve 33 is a diaphragm-type valve provided with a bleed as are also valves 19 and 23, and gas under pressure is controllably supplied to the diaphragm side of valve 33 through a conduit 41. Gas under pressure, in turn, is supplied to control unit 39 through a conduit 43 that communicates with and receive gas under pressure from vent conduit 15.

A temperature sensor 45 is located within the material storage portion of compartment 1 and controls control unit 39. When the temperature in compartment 1 rises undesirably high, temperature senser 45 reacts quantitatively and actuates control unit 39 variably in effect to open conduit 41 a suitable amount to the relatively high pressure fluid in conduit 43, so that pressure is supplied to the diaphragm of valve 33 to open valve 33 a suitable amount so that liquefied gas will be forced from container through conduit 13 into conduit 35 and then into spray header 37 at a suitable flow rate, whence it is sprayed in liquid phase over material in chamber 1 to cool the material. Conversely, when the temperature in compartment 1 has thus been lowered to a desired temperature level, temperature senser 45 reacts to this lower temperature by actuating control unit 39 to shut ofi conduit 41 from communication with conduit 43, whereupon the pressure in conduit 41 bleeds off and the pressure above the diaphragm of valve 33 accordingly drops and valve 33 closes to shut off the flow of liquid from container 5 to spray header 37.

Valve 33 is not simply a two-position open-closed valve, but rather is responsive to a variety of pressures in conduit 41 to open to a variety of positions to admit more or less fluid to spray header 37 thereby to respond to various temperatures in the compartment with greater sensitivity than if valve 33 were simply to hunt between fully open and fully closed positions. Temperature senser 45 and control unit 39 are by themselves quite conventional in construction and need not be described in greater detail here.

Also disposed in conduit 43 is a valve 47 operated by a plunger 49 in contact with door 3 of compartment 1. Valve 47 is open in the position shown in the drawing, in which door 3 is closed. But when door 3 opens,

plunger 49 is released to move away from valve 47, thereby closing valve 47 and shutting off the flow of gas under relatively high pressure through conduit 43. As conduit 43 is the only source of relatively high pressure fluid for control unit 39 and conduit 41, the closing of valve 47 will drop the pressure on the diaphragm side of valve 33, thereby closing valve 33 and shutting oif the flow of liquid to spray header 37, regardless of what signal temperature senser 45 sends to control unit 39. In other words, when door 3 is opened, liquid cannot be supplied to spray header 37 even though the temperature in compartment 1 rises relatively quite high.

Conduit 43 is also provided with a manually operated valve (not shown) such that when the operator enters the compartment he can close conduit 43 manually, so that if door 3 should accidentally swing shut behind him he will not be sprayed with liquefied gas.

During normal operation, valves 19 and 23 will be closed and valve 33 will open only to permit the withdrawal of liquid from container 5. Of course, there will be a certain heat leak into container 5 despite insulation 7, with the result that the pressure within container 4 inevitably builds up. Accordingly, a conduit 51 is provided which communicates between vent conduit 15 and the interior of compartment 1, and that is controlled by a pressure relief valve 53 set at a desired maximum pressure for container 5, say, 25 p.s.i. gage, so that upon attainment of that predetermined maximum pressure, valve 53 will open to vent the excess vapor from container 5 to the interior of compartment 1 thereby further cooling compartment 1.

To enable those skilled in this art to practice the invention, the following illustrative example of the use of apparatus in the practice of the method of the present invention will be given:

Say the invention is embodied in a delivery truck for frozen material such as frozen foods. At the beginning of the days deliveries, the truck is loaded and liquid nitrogen is introduced through conduit 9 past check valve 11 into conduit 13 and thence into container 5. Valves 19, 23 and 33 are initially closed. As the liquid nitrogen strikes the relatively warm container 5, a quantity of liquid nitrogen boils off and escapes through conduits 15 and 25, thereby opening valve 19. The gas proceeds past open valve 19 into'branch conduit 17 and thence into conduit 35 and through spray header 37.

This nitrogen vapor has boiled off at its boiling point and is quite cold and pre-cools a substantial portion of the apparatus and the air space within the compartment. Alternatively, conduit 17 can communicate directly with the interior of the compartment, in which case the cold gas by-passes conduit 35 and spray header 37.

Of course, during this pre-cooling operation, door 3 will be closed. The operator who performs the filling operation with liquid nitrogen may have no really good Way to know when the filling operation is completed. Liquid level gages in the form of sight glasses or floats are of little value at this stage of the operation, because the apparatus is not at thermal equilibrium and the contents of container 5 may be boiling and in any event are greatly agitated by the filling operation. It is only later, during the day, when the apparatus is at thermal equilibrium and the body of liquid nitrogen in container 5 is lying quiescent that such liquid level gages will give an accurately indicative reading. With no way of accurately determining the end point of the filling operation, the operator will quite likely overfill, with the result that a great deal of liquid nitrogen may be poured into the compartment 1 before the operator realizes that the filling operation is completed. This is not only wasteful but also rather dangerous. Although compartment 1 is provided with pressure relief valve means (not shown) by which excess vapor pressure in compartment 1 is vented to the ambient atmosphere, nevertheless, the release of a large body of boiling liquid nitrogen Within compartment 1 is obviously quite dangerous.

Therefore, when the operator estimates that the end point of filling may be approaching, he can close valve 19 and open valve 23. He has pre-cooled the system during the time that valve 19 was open; and when he close-s valve 19 he is able to test for the end point of filling, for as soon as container 5 is full, excess liquid Will be able to escape only through conduit 15, which communicates with the outside of the truck. As soon as liquid nitrogen emerges from conduit 15 outside the truck, the operator can see this condition and discontinue filling.

Alternatively, container 5 may be provided with liquid level gage means responsive to difierences in pressure between the top and the bottom of the container thereby to determine the hydrostatic head in the container and indicate the depth of the liquid. Such differential pressure gages can be largely immune to the effects of liquid agitation.

With container 5 full of liquid nitrogen and valves 19 and 23 closed, the truck is ready to begin the days deliveries. As the operator drives from place to place, heat leak into the interior of compartment 1 will continuously cause the temperature to rise, so that from time to time temperature senser 45 will signal control unit 39 to open valve 33 an appropriate amount to cause liquid nitrogen to spray out of spray header 47 at a suitable flow rate directly on the material carried in compartment 1 of the truck. As soon as the temper ature drops sufiiciently, senser 45 signals control unit 39 to close valve 33 or to reduce the flow rate through valve 33. If the periodic withdrawals of liquid from container 5 are not enough to keep the pressure in container 5 at a desirably low level, then pressure relief valve 53 automatically opens to vent the excess vapor under pressure to the interior of compartment 1.

Whenever the operator opens door 3 to remove material from compartment 1, valve 47 closes and valve 33 is therefore maintained closed, so that the operator cannot be showered with liquid nitrogen regardless of how high the temperature rises in compartment 1 when the door is open. And as was previously noted, a manually controlled valve can be provided in conduit 43, which the operator can manually close and open when he enters and leaves the compartment, respectively. Of course, as soon as door 3 is closed again and valve'47 is opened by plunger 41 having been contacted by door 3, then temperature senser 45 is again effective to operate control unit 39 to open valve 33, so that a rise in temperature can be quickly corrected by a direct spray of liquid nitrogen.

It should also be noted that the provision of pressure relief valve 53 tends to assure that the fluid in container 5 will be maintained under pressure, so that the pressure of fluid in container 5 tends to be adequate to force liquid through conduit 13 and out of spray header 37. At the same time, the pressure of the vapor in conduit 15 will be maintained at a sufficiently high level that the pressure of the vapor withdrawn through conduits 25 and 43 will be adequate to actuate the diaphragm valves 19, 23, and 33. Finally, it should be noted that all of the main flow conduits of the present invention are disposed substantially entirely internally of the compartment so that they can be well insulated against heat influx. Only the pneumatic control conduits extend far away appreciable distance outside the insulation.

From a consideration of the foregoing disclosure, therefore, it will be evident that all of the initially recited objects of the present invention have been achieved.

Although the present invention has been described and illustrated in connection with preferred embodiments, it is to be understood that modifications and variations may be resorted to without departing from the spirit of the invention, as those skilled in this art will readily understand. For example, instead of being pneumatically actuated, the valves and other controls of the present invention can be electrically actuated or hydraulically actuated or, in certain cases, mechanically actuated. These and other modifications and variations are considered to be within the purview and scope of the present invention as defined by the appended claims.

What is claimed is: 1. The method of cooling a compartment to be refrigerated, comprising the steps of introducing into a container a normally gaseous liquefied gas, withdrawing vapor from an upper portion of .the container during the introduction step and conducting the same through a passageway into the interior of the compartment, discontinuing the flow of vapor through said passageway, and thereafter withdrawing liquefied gas from a lower portion of said container and conducting the withdrawn liquefied gas through another passageway into the interior of the compartment, the last-named step occurring at least in part after the end of said introduction step.

2. Refrigeration apparatus, comprising means defining a compartment having a door, a container for a body of liquefied gas having a boiling point below the temperature of the compartment,

valve-controlled conduit means communicating with an upper portion of the container for conducting vapor from said liquefied gas into the interior of the compartment,

means for discharging liquefied gas from said body into the compartment,

means disabling the last-named means when the door is opened, and

means in fluid communication with an upper portion of said container for utilizing the pressure of vapor from said liquefied gas in the container to operate said disabling means.

3. Refrigeration apparatus, comprising means defining a compartment to be refrigerated,

a container for a body of liquefied gas having a boiling point below the temperature of the compartment,

means for discharging liquefied gas from said body into the interior of the compartment to refrigerate the compartment,

valve-controlled conduit means communicating with an upper portion of the container for conducting vapor from said liquefied gas into the interior of .the compartment,

vapor discharging means for discharging vapor of the liquefied gas from an upper portion of the container to the exterior of the compartment, and

means in fluid communication with an upper portion of said container, for utilizing the pressure of vapor from said liquefied gas in the container to operate said vapor discharging means.

4. Refrigeration apparatus, comprising means defining a compartment to be refrigerated,

a container for a body of liquefied gas having a boiling point below the temperature of the compartment,

means for discharging liquefied gas from said body into the interior of the compartment to refrigerate the compartment,

vapor discharging means for discharging vapor of the liquefied gas from an upper portion of the container to the interior of the compartment, and

means in fluid communication with an upper portion of said container for utilizing the pressure of vapor from said liquefied gas in the container to operate said vapor discharging means.

5. Refrigeration apparatus, comprising means defining a compartment .to be refrigerated,

a container for a body of liquefied gas having a boiling point below the temperature of the compartment, first conduit means, communicating with an upper portion of the container for conducting vapor from said liquefied gas into the interior of the compartment, first valve means controlling said first conduit means, means in fluid communication with said container, for utilizing vapor of said liquefied gas under pressure of fluid in the container to operate said first valve means, second conduit means, communicating with a lower portion of the container for conducting liquefied gas into the interior of the compartment, and

second valve means controlling said second conduit means.

6. Refrigeration apparatus as defined in claim 5, and further comprising means in fluid communication with said container for utilizing vapor of said liquefied gas under pressure of fluid in the container to operate said second valve means.

7. Refrigeration apparatus as defined in claim 6, and further comprising third conduit means, communicating with an upper portion of said container for conducting excess liquefied gas to the exterior of the compartment.

8. Refrigeration apparatus as defined in claim 7, wherein said first conduit means and said third conduit means are branches of a single conduit means which communicates with an upper portion of the container.

References Cited by the Examiner UNITED STATES PATENTS 2,479,840 8/1949 Johnson 62514 X 3,005,321 10/1961 Devery 62-186 3,109,296 11/1963 Williamson 62-514 X 3,114,247 12/1963 MacLean 62-514 X MEYER PERLIN, Primary Examiner. 

1. THE METHOD OF COOLING A COMPARTMENT TO BE REFRIGERATED, COMPRISING THE STEPS OF INTRODUCING INTO A CONTAINER A NORMALLY GASEOUS LIQUEFIED GAS, WITHDRAWING VAPOR FROM AN UPPER PORTION OF THE CONTAINER DURING THE INTRODUCTION STEP AND CONDUCTING THE SAME THROUGH A PASSAGEWAY INTO THE INTERIOR OF THE COMPARTMENT, DISCONTINUING THE FLOW OF VAPOR THROUGH SAID PASSAGEWAY, AND THEREAFTER WITHDRAWING LIQUEFIED GAS FROM A LOWER PORTION OF SAID CONTAINER AND CONDUCTING THE WITHDRAWN LIQUEFIED GAS THROUGH ANOTHER PASSAGEWAY INTO THE INTERIOR OF THE COMPARTMENT, THE LAST-NAMED STEP OCCURING AT LEAST IN PART AFTER THE END OF SAID INTRODUCTION STEP. 